1. Field of the Invention
The present invention generally relates to a chip package structure. More particularly, the present invention relates to a microelectromechanical system (MEMS) package structure.
2. Description of Related Art
Microelectromechanical system (MEMS) is a microelectromechanical device fabricated in a microminiaturized package structure, and the fabricating technique thereof is quite similar to the technique of fabricating integrated circuits (ICs). However, interactions, for example, about mechanics, optics, or magnetic force between the MEMS device and surrounding environment are more than that of the conventional IC.
The MEMS device may include micro-sized electromechanical components (for example, switches, mirrors, capacitors, accelerometers, sensors, capacitive sensors, or actuators etc.), and the MEMS device may be integrated with the IC in a manner of single block, thereby greatly modifying insertion loss or electrical isolation effect of the overall solid-state device. However, in the macroscopic world of the entire package structure, the MEMS device is extremely fragile and may be impacted by slight static electricity or surface tension at any moment to cause failure. Therefore, in order to prevent the MEMS device from contaminations or damages, usually the MEMS device is sealed in a space between the chip and the lid.
FIG. 1 is a schematic view of a conventional MEMS package structure. Referring to FIG. 1, a conventional MEMS package structure 10 comprises a cover plate 12, a chip 14, a sealant 16 and MEMS devices 18. The cover plate 12 is fixed on the chip 14 with the sealant 16, such that the MEMS devices 18 are sealed in a space between the chip 14 and the cover plate 12.
However, in the conventional MEMS package structure 10, although the space between the chip 14 and the cover plate 12 is sealed by the sealant 16, the sealant 16 may crack and the moisture may permeate into the space between the chip 14 and the cover plate 12 easily after using a period of time in high humidity environment due to a large gap between the cover plate 12 and the chip 14, thereby affecting the normal operation of the MEMS devices 18.